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Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
- From: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
- To: dewar at gnat dot com
- Cc: autoconf-patches at gnu dot org, bug-gnulib at gnu dot org, dewar at adacore dot com, eggert at cs dot ucla dot edu, gcc at gcc dot gnu dot org, gdr at integrable-solutions dot net
- Date: Sat, 30 Dec 2006 20:54:23 EST
- Subject: Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
- References: <20061231010207.C200A48CC4B@nile.gnat.com>
> Gaby said
>
> K&R C leaves arithmetic overflow undefined (except for unsigned
> types), in the sense that you get whatever the underlying hardware
> gives you. If it traps, you get trapped. If it wraps, you get wrapped.
>
> Is that really what the K&R book says, or just what compilers typically
> did? My memory is that the K&R book leaves it undefined period, but it's
> a long time since I read it!
I found my copy of K&R (Second Edition). Page 200: "The handling of overflow,
divide check, and other exceptions in expression evaluation is not defined
by the language. Most existing implementations of C ignore overflow in
evaluation of signed integral expressions and assignments, but this behavior
is not guaranteed."